The average sugarcane yield in Sindh is very low.
Recommendations for N, P and K requirements have been prescribed, but adequate
attention to other nutrients has not adequate, and important nutrients may be
limiting the optimum growth and yield of sugarcane. Besides adequate level of
nutrients at different growth stages is also an important aspect of plant
growth, which requires due consideration. Crop-logging may be of great help to
determine the adequate levels of different nutrients for good plant growth and
high yield. The concept of crop-logging was developed by Clements of USA for the
growing of sugarcane in Hawaii, where the fertilizer requirements of this crop
are greatly influenced by weather and climate.

The crop log is a record of the crop's progress from its
start until harvest and is made up of certain physical and chemical measurement
and observations which serve as a guide to its handling. Adequate nutrition of
augarcane results in optimum growth and development of the plant with high sugar
yield. The balance for the low sugar yield in Sindh is usually put on the
existing varieties, with no considerations of the nutritional status. In order
to obtain a guide line for planned research programme, it was essential to make
a nutritional survey of the sugarcane crop of Sindh cane zones. The ultimate aim
of this technique is to ascertain a guide line for future nutritional research
programme based on crop-logging of sugarcane.

Eight months old sugarcane plants of four commercially grown
varieties (PR-1000, BL-4, CP-68-1067 and L-116) were collected from the
experimental farm of NIA, Tandojam and chopped into double budded sets of about
15 cm in length. These sets were then dipped in 0.8% benlate solution for 3
minutes before planting and then sown to desert sand beds of pot-house in the
month of November. Six sets were sown to each bed measuring about 2.7% square
meter. The beds were irrigated with tap water and after 20 days when the
seedling had emerged almost in every variety, the following treatments were
started. (1) Control (full Hoagland solution) (2) minus nitrogen (3) minus
phosphorus and (4) minus potassium.

In the control bed, all the major and minor nutrient elements
necessary for the growth of sugarcane plants were added as salts. In the minus
treatments all the salts were added to the individual tanks except those
containing N, P and K. There were two replicates of each treatment making a
total of 32 beds. The beds were irrigated every week and the necessary salts
were added to the tanks when necessary as determined from periodical analysis of
the culture solution. The third fully expanded leaf from three plants of each
variety were collected after 75 days of sowing and thereafter every monthly
making a total of ten harvests. The fresh (two harvests) and dry weights of
plant leaves were recorded and the samples were analyzed for N, P, K, Ca and Na
contents. The deficiency symptoms of N, P, K were also recorded as and when they
appeared. The N deficiency symptoms were most distinct, where plants were
yellowish green in colour, the stalks were smaller in diameter and slight
reddish colour developed on the dry lead portion of the stalk.

The plants had very little tillering in most of the
varieties. Compared to control treatment the P deficient plants had much smaller
and fewer leaves with deeper green colour. The most significant affect of
inadequate P was its effect on tillering, and there were few tillers with
slender stalks in most of the varieties. In the absence of K, the first symptoms
of K-deficiency consisted of a retardation growth with distinctly slender stalks
followed by a distinct yellowing of the leaves, which was accentuated at the
tips and margins. This marginal yellowing was followed later on by death or
firing of the affected areas, a condition also referred to as marginal scorch.
The plants in the complete nutrient solution (control) were healthy, well
branched and normal green in colour. The growth for about three months was not
affected very much in the minus nutrient treatments, but the effects of the
absence of particular nutrients became visible thereafter. The variety BL-4
produced the maximum leaf dry wt in all the treatments followed by L-116 PR-1000
and CP-68 in that order.

The analysis of the plant leaves at the earlier harvested
showed no marked differences in the content of N, P, K of the leaves from the
minus treatments compared with those from the control plants. At the later
stages of growth, when N, P, K deficiency symptoms also appeared the analysis
indicated that the deficient leaves contained relatively low quantities of the
respective nutrients (NPK) as compared to the healthy (control) ones, which
apparently resulted in the retarded growth of plants.

Nutrient requirements of sugarcane: The sugarcane crop has
gained a considerable importance in the province of Sindh during the last
fifteen years or so. It has now become one of the most promising cane crops of
this region. With the establishment of sugar mills in the southern zone, there
has been a phenominal rise in the average of this crop. Though the average has
increased from 17000 acres at the time of independence to almost 24x105 acres
now, yet the yield of cane and the recovery of sugar have remained the lowest in
the world. The yield of sugar is hardly about one or two tons per acre as
compared to 11 tons in Hawaii, about 7 tons in Java (Indonesia), 3.5 tons in
Mauritius and Australia about 3.0 tons in Cuba, Philippines and India. The
causes of such a poor yield have to be examined.

Balanced nutrition of cane plant results in good growth and
high yield. Numerous attempts have been made to predict the nutrients
requirement of sugarcane. These involved both soil and diagnostic tissue testing
methods. Critical levels of different nutrients are estimated after intensive
fertilizer experiments in the field and pots as well. Much emphasis has been
given to diagnostic tissue analysis as a guide for fertilizer application in
cane crop. Tissue analysis helps in knowing whether the crop is deficient in
applying additional amounts of fertilizers. Visual symptoms develop only when
the nutrient deficiency becomes acute and then it is too late to correct the
same. Clements (1960 ) in Hawaii has developed a foliar diagnostic technique
known as Crop-logging of sugarcane.

Crop logging aims at portraying all the important factors of
plant physiology which the crop experience from the time it is started until it
is harvested and in such a precise and simple manner that it can be used as a
guide for the profitable production of cane and sugar. In this method plant
samples are collected every 5 weeks from 3 months of age, analyzed and
determined whether the crop needs additional fertilizers and the application of
fertilizers influences both yield of cane and its wide quality in respect of
sucrose content.

Clements (1960 ) in his crop-logging has established the
critical levels of different nutrients, leaf N 2.2 to 2.5%, P. K, Ca and Mg
contents of sheath expressed as percent sugar free-dry matter as 0.08%
respectively. When the level of any of the above nutrient falls below the
critical, additional fertilizers increase cane and sugar yields. He suggests
that the sheath Mn content below 20 ppm is the possible range of deficiency and
that above 150-200 ppm the toxic. For a one year crop in British Guyiana, Evans
(1967) reported the 4th leaf lamina as suitable diagnostic tissue for all the
essential nutrients. He established that during the "boom stage" of
growth the leaf lamina of plant crop at 3 months and ratton at 2 months should
contain 2.4-2.5% N. Phosphorus should be 0.21% throughout the growth period in
plant crops as well as in rattons. Critical level for K is 1.25% in the dry
matter during the active growth. While those for Ca and Mg are 0.13-0.15% Ca and
0.06-0.08% Mg respectively. He further suggests that adequate levels of
different micro-nutrients in the leaf lamina are as follows:

Adequate nutrition of cane results in optimum growth and
development of the plant with high sugar yield. The balance for the low sugar
yield in Sindh is usually put on the existing varieties, with no considerations
of the nutritional status. In fact, inadequate nutrition is definitely one of
the major factors causing the low yield of sugar. Inadequate literatures on the
nutritional status of the existing varieties is one of the limitations in
undertaking nutritional research. In order to obtain a guide line for planned
research programme, it was essential to make a nutritional survey of the
sugarcane crop of Sindh cane zones. The ultimate aim of this is to ascertain a
guide line for future nutritional research programme based on crop logging.